Britain’s option for a block opt-out from most EU crime and policing policy was negotiated as part of the Lisbon treaty in 2007. EU co-operation in these areas is based on approximately 130 ‘justice and home affairs’ (JHA) agreements. Most of these are currently inter-governmental ‘framework decisions’ and cover how police, prosecutors and courts across the EU should co-operate to investigate crime, organise extraditions, share criminal records and exchange evidence.

However, the Lisbon treaty allows the ECJ to treat such decisions in the same manner as single market regulation from December 2014 onwards. This means that, for the first time, the European Commission will be able to take to court those countries which fail to implement police and justice decisions made collectively by EU interior and justice ministries. And judges in the ECJ can ensure that these decisions are evenly applied throughout the EU by fining those countries which do not comply and handing down legal advice to national courts. Hugo Brady explains why this may be a mistake.